This invention relates to a sound insulating apparatus to be installed in a communicating port for communicating two spaces partitioned with respect to each other and adapted to diminish a sound propagating from one space to the other through the communicating port.
The sound insulating apparatus according to the present invention is installed in a ventilator of various architectures such as, for example, a house, shop, office, workshop, etc., in order to prevent an outside noise to come into the architecture through the ventilator, or an inside noise to come out of the architecture through the ventilator, but to allow air to pass freely therethrough.
As a gimmick to pass only air and insulate a sound as mentioned above, heretofore, there has been widely practiced as follow. That is, a sound absorbing material such as a glass wool is attached to the internal side of a duct. However, in such a conventional sound insulating apparatus as mentioned, a sound which advances straight forward along the elongated direction of the duct is absorbed by a sound absorbing material disposed parallel thereto. Therefore, it was difficult to obtain a sufficient effect of sound insulation.
Also, there are others which attempt to damp a sound by bending the duct at right angles, or by providing a sound absorbing chamber in the duct so that the sound will be damped by means of enlarging or reducing its passage. However, they were effective only for a noise of particularly limited frequency range, and no sufficient muffling effect could be expected for a noise of wide frequency band width.
Furthermore, all of the above mentioned conventional sound absorbing apparatuses had such disadvantages as that the passage resistance is increased due to the long duct, and that the weight is increased due to the large external dimension thereof.